Place flour in a shallow pan. Place buttermilk in a shallow bowl. Mix cornmeal and cracker meal well. Place mixture in a shallow dish. Dredge onion rings in buttermilk the in flour to coat. shake off excess flour Set aside for 10 minutes. Then dredge in buttermilk again then corn meal mixture to coat. Let sit 5 minutes. the deep fry in oil until golden brown. Drain on paper towels.